Study on the formation process of MoO3/Fe2(MoO4)3 by mechanochemical synthesis and their catalytic performance in methanol to formaldehyde

Mechanochemical method has applied to the green preparation of iron-molybdenum catalyst efficiently, and their catalytic performance was evaluated by the oxidation of methanol to formaldehyde. In order to investigate the formation process of iron-molybdenum catalyst based on mechanochemical method, various characterization techniques have been employed. Results indicate that iron-molybdenum catalyst could not be generated during ball milling process without calcining, and calcination is crucial step to regulate the ratio of MoO₃ and Fe₂(MoO₄)₃. For the formation of MoO₃ and Fe₂(MoO₄)₃ phase, 180 °C could be the key turning temperature point. Fe₂(MoO₄)₃ and MoO₃ phases are concurrently emerged when Mo/Fe atomic ratio exceeds 1.5. The aggregation of Fe₂(MoO₄)₃ is severe with the increasing calcination temperature. Fe₂(MoO₄)₃ is stable below 600 °C, while MoO₃ phase could be subliming with the increasing temperature. The catalytic performance of iron-molybdenum catalyst has closely correlation with the phase compositions, which can be controlled by synthesis temperature and Mo/Fe molar ratio. The iron-molybdenum catalyst with Mo/Fe atomic ratio of 2.6 calcined at 500 °C for 4 h showed the best methanol conversion (100%) and formaldehyde yield (92.27%).